Retinitis pigmentosa is a group of hereditary retinal diseases that often lead to blindness; an estimated 50,000 to 100,000 people are affected in the United States. More than 10,000 patients are on file in this research center. Considerable progress has been made in defining the gene defects that cause these conditions, but the course of disease for most subgroups is not known. We propose to mode the course of disease based on data from our large number of patients with multiple visits and up to 32 years of follow-up. We will then use the optimal model as a template to define the rates of progression in patients with two relatively common subgroups of retinitis pigmentosa caused by USH2A or RPGR mutations, respectively. Rates of progression will be monitored with respect to visual acuity, visual field area and sensitivity, and full-field electroretinogram amplitude. We will perform genotype/phenotype correlations to see if rates of progression can be related to category of mutation. These data should provide guidelines for estimating long-term visual prognoses in patients with USH2A or RPGR mutations and provide a framework for considering gene-specific therapies that may arise in the future for these patients. We also propose to compare the course of disease in affected sibpairs, regardless of mutation, to facilitate identification of nutritional and other non-genetic factors that may affect rates of progression. Information derived from this research could reveal factors that are associated with a slower or faster course of disease with potential implications for therapy. We will also continue genotype/phenotype correlations in patients with newly defined gene defects.